Main menu state now requires pressing <enter> to continue

This is the first commit on a long series of making the Main Menu
Main Menu now uses the "Loaded" font and has a centralized text

"Loaded" is free to use and looks awesome
Main Menu now has the game logo
Created a "Menu" class that will abstract user selections

For now the Main Menu is kinda trashy... Will improve on next commits
Made the items inside "Menu" to be relatively positioned between each other
"Menu" now highlights the current item
Made possible to select "next" and "previous" items on the Menu
Generalized the Menu's color and highlight color
Now the menu item's selection wraps up

Added "first()" and "last()" methods to the Menu selection.
Menu items can actually get selected now

By pressing "Enter" you can react according to the current Menu item
Made easier to read on the menu items

Created tiny local enum so we can easily add new items to the main menu
Menu now reacts to "first" and "last" keys
Generalized the Menu's way of changing the current item
Menu selection screen now has sound

When you change an item it plays a sound - which should get improved in
time
Renamed "Menu" class to "ButtonList" and separated "MenuItem" to "Button"
Merge pull request #3 from alexdantas/making-gui

Made a Main Menu screen with selectable Buttons